Electric fan system for vehicle

ABSTRACT

An electric fan system for a vehicle including two electric fans ( 10, 20 ) arranged in parallel in a vehicle width direction so as to blow cooling air to a radiator ( 100 ) and a condenser ( 110 ), wherein the electric fans are driven by a brushless motor ( 12 ) and a brush motor ( 22 ), a first drive voltage V 1  for driving the brushless motor is set so as to increase in accordance with an increase of a water temperature (Tw) of the radiator or a coolant pressure (Pc) of the condenser, and simultaneously a second drive voltage V 2  for driving the brush motor is set so as to increase monotonously as a value lower than the first drive voltage, whereby the two electric fans can operate simultaneously at all times, unevenness of the distribution of the flow rate can be reduced, and the drive voltage of the brush motor is reduced, so the lifetime can be extended and, further, provision is made of an electronic control unit ( 40   a ) for preferentially operating the electric fan ( 10 ) driven by the brushless motor over the electric fan ( 20 ) driven by the brush motor based on the temperature of the engine cooling water and the electric fan ( 10 ) driven by the brushless motor is designed to cool by cooling air other vehicle-mounted parts besides the radiator ( 100 ) and the condenser ( 110 ), specifically for example the ECU box ( 410 ).

CROSS REFERENCES TO RELATED APPLICATIONS

This application is based upon and claims priorities of Japanese Patent Application No. 2004-352743, filed in the Japan Patent Office on Dec. 6, 2004, and Japanese Patent Application No. 2004-376269, filed in the Japan Patent Office on Dec. 27, 2004, the contents being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric fan system for a vehicle which uses an electric fan to generate cooling air.

2. Description of the Related Art

In the past, as an electric fan system for a vehicle, there has been one which used an electric fan to circulate cooling air to a radiator for cooling engine cooling water and a condenser for vehicle air-conditioning so as cool the radiator and condenser.

In general, in a taxi, bus, or other vehicle with a high frequency of use of the electric fan, a sufficient fan capacity, rectification of the distribution of air blown to the radiator, extension of the lifetime of the electric motor, and reduction of the cost are demanded.

For example, when applying this electric fan system for a vehicle to a taxi, bus, or other vehicle with a high frequency of use of the electric fan, an electric motor with a large rated capacity has been employed as the electric motor of the electric fan and this electric motor has been operated by a power lower than the rated capacity so as to keep the deterioration of the electric motor itself to a minimum and extend the lifetime of the electric motor.

However, in this case, by employing an electric motor with a large rated capacity, there is a possibility of inviting not only an increase in cost, but also an increase in weight.

Further, in an electric motor for an electric fan, it is known to employ a brushless motor so as to extend the lifetime of the electric motor, but when the dimension of the radiator in the vehicle width direction (left-right direction of vehicle) is larger than the dimension of the rotor of the electric fan in the vehicle width direction, with just a single electric fan, the distribution of air blown to the radiator would deteriorate and parts of the radiator where cooling air is not blown would end up arising thereby inviting a drop in the cooling efficiency of the radiator and in turn deterioration of the fuel economy.

As opposed to this, by employing two or more electric fans using brushless motors, it would become possible to rectify the distribution of blown air to the radiator and send sufficient cooling air to the radiator, but the control circuit for controlling the brushless motors would become complicated in configuration and a further increase in cost would be invited.

Therefore, the assignees proposed in a prior Japanese Patent Application No. 2003-273458 an electric fan system for a vehicle designed to keep down the increase in cost and extend the lifetime. The invention of this prior application provides a first electric fan for circulating cooling air to the radiator and condenser by a brushless motor and a second electric fan for circulating cooling air by a brush motor. For example, when it is judged that the temperature of the cooling water circulating through the radiator is less than a predetermined value, just the first electric fan is operated, while when it is judged that the temperature of the cooling water is the predetermined value or more, both the first and second electric fans are operated.

In this electric fan, when the temperature of the cooling water becomes higher than a first threshold value, only the first electric fan is operated. When the temperature of the cooling water exceeds a second threshold value higher than the first threshold value (>first threshold value), the first and second electric fans are both operated. Therefore, the first electric fan is operated preferentially compared with the second electric fan. Accordingly, wear of the second electric fan, that is, wear of the brush motor, is suppressed and the lifetime is extended.

That is, if the temperature of the cooling water does not become the predetermined value or more, the second electric fan does not operate thereby reducing the operating rate of the brush motor and reducing the wear of the brush motor, that is, extending the lifetime of the brush motor. Therefore, by jointly employing a brushless motor free from problems in terms of motor lifetime and a brush motor extended in lifetime, it is possible to reduce the total cost of the electric fan system for a vehicle and extend its lifetime.

However, in the invention of the prior application, when the temperature of the cooling water is less than the predetermined temperature, the brush motor stops operating, but during this time the distribution of the flow rate in the vehicle width direction of the radiator becomes uneven. In the end a large power is required for obtaining the same performance (heat dissipation) with just the first electric fan. Further, at the parts usually blown upon by the stopped second electric fan, hot air sneaks around (flows back) from the high temperature, high pressure engine side to the vehicle front direction (radiator front side), the temperature in front of the heat exchanger rises, and the cooling performance and air-conditioning performance drop.

Further, in the engine compartments of recent vehicles, aside from the radiator and condenser, the electronic control unit, headlamps, rubber engine mounts, and other parts mounted in the vehicle also have to be cooled. In the above electric fan system for a vehicle using a brushless motor and brush motor, however, no consideration was given to cooling these other vehicle-mounted parts.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide an electric fan system for a vehicle enabling an extension of the lifetime while reducing the unevenness of the distribution of the flow rate.

A second object of the present invention is to provide an electric fan system for a vehicle designed to enable cooling of not only the radiator and condenser, but also other vehicle-mounted parts while extending the lifetime.

To achieve the first object, according to a first aspect of the present invention, there is provided an electric fan system for a vehicle which circulates cooling air to a heat exchange unit provided with a radiator for cooling cooling water circulating inside a water-cooled engine for vehicle operation and a condenser for cooling a coolant circulating inside a refrigeration cycle apparatus, the system provided with a brushless motor driven by a first drive voltage, a first electric fan for circulating cooling air to the heat exchange unit by the brushless motor, a brush motor driven by a second drive voltage, a second electric fan for circulating cooling air to the heat exchange unit by the brush motor, and a control device for supplying the brushless motor with the first drive voltage so that the first drive voltage monotonously increases up to a first maximum drive voltage in accordance with a rise in temperature of the cooling water and for supplying the brush motor with the second drive voltage so that the second drive voltage monotonously increases up to a second maximum drive voltage in accordance with a rise in temperature of the cooling water and becomes a voltage lower than the first drive voltage based on the detection output from a temperature sensor for detecting the temperature of the cooling water.

According to the first aspect, the drive voltage of the brushless motor constituted by the first drive voltage is made to monotonously increase in accordance with a rise in temperature of the cooling water and the drive voltage of the brush motor constituted by the second drive voltage is made a voltage lower than the first drive voltage and is made to monotonously increase in accordance with a rise in temperature of the cooling water. Therefore, when the first electric fan of the brushless motor is operating, the second electric fan of the brush motor does not stop and is also simultaneously operating, so hot air sneaking its way to the parts meant to be blown on of the second electric fan in the heat exchange unit is avoided and therefore the unevenness of the distribution of the flow rate can be reduced and the cooling efficiency of the heat exchange unit can be raised.

Further, in the process of increasing the drive voltage along with a rise in the temperature of the cooling water, since the drive voltage of the brush motor constituted by the second drive voltage is set lower than the drive voltage of the brushless motor constituted by the first drive voltage, the lifetime of the brush motor can be extended and the lifetime of the electric fan system can be prolonged.

Note that according to a second aspect of the present invention, when the temperature of the cooling water is a temperature of a temperature threshold value or more, the first and second maximum drive voltages may be set to become constant values.

According to a third aspect of the present invention, instead of the rise in the temperature of the cooling water of the first aspect of the invention, the first and second drive voltages are made to monotonously increase in accordance with the rise of the pressure of the coolant. Therefore, in the same way as the first aspect of the invention, the drive voltage of the brushless motor constituted by the first drive voltage is made to monotonously increase in accordance with a rise in the coolant pressure and the drive voltage of the brush motor constituted by the second drive voltage is made a voltage lower than the first drive voltage and is made to monotonously increase in accordance with a rise in the coolant pressure. Therefore, when the first electric fan of the brushless motor is operating, the second electric fan of the brush motor also simultaneously operates without stopping, so hot air sneaking its way to the parts meant to be blown on of the second electric fan in the heat exchange unit is avoided and therefore the unevenness of the distribution of the flow rate can be reduced and the cooling efficiency of the heat exchange unit can be raised.

Further, in the process of increasing the drive voltage along with a rise in the coolant pressure, since the drive voltage of the brush motor constituted by the second drive voltage is set lower than the drive voltage of the brushless motor constituted by the first drive voltage, the lifetime of the brush motor can be extended and the lifetime of the electric fan system can be prolonged.

According to a fourth aspect of the present invention, when the pressure of the coolant is a pressure of a pressure threshold value or more, the first and second maximum drive voltages can be set to become constant values.

According to a fifth aspect of the present invention, both the first and second electric fans are axial flow fans. By making the fan diameters substantially equal, it is possible to make the distribution of the flow rate to the entire surface of the heat exchange unit uniform and possible to raise the cooling efficiency of the heat exchange unit.

To achieve the second object, according to a sixth aspect of the present invention, there is provided an electric fan system for a vehicle which circulates cooling air to a heat exchange unit provided with a radiator for cooling cooling water circulating inside a water-cooled engine for vehicle operation and a condenser for cooling a coolant circulating inside a refrigeration cycle apparatus, the system provided with a first electric fan for circulating cooling air to the radiator and condenser by operation of a brushless motor, a second electric fan for circulating cooling air to the radiator and condenser by a brush motor, and a control means for operating the first electric fan preferentially over the second electric fan based on a state of either the cooling water and the coolant, the first electric fan being designed to cool other vehicle-mounted parts than the radiator and condenser by cooling air.

According to the sixth aspect of the present invention, since the first electric fan is operated preferentially over the second electric fan, the wear of the second electric fan, that is, the wear of the brush motor, can be suppressed. Further, since the first electric fan is designed to cool other vehicle-mounted parts besides the radiator and condenser by cooling air, the lifetime is extended and other vehicle-mounted parts can also be cooled.

Here, according to a seventh aspect of the present invention, there is provided the electric fan system for a vehicle as set forth in the sixth aspect of the invention wherein the control means determines the flow rate of cooling air by the first electric fan based on both the state of one of the cooling water and the coolant and the temperature of the other vehicle-mounted parts, so the other vehicle-mounted parts, radiator, and condenser can be suitably cooled.

According to an eighth aspect of the present invention, the first electric fan is designed to blow air toward locations different from the locations where the other vehicle-mounted parts are arranged.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein:

FIG. 1 is a schematic view of the electric fan system for a vehicle according to an embodiment of the present invention;

FIG. 2 is a view of the arrangement of a radiator and a condenser according to the electric fan system for a vehicle of FIG. 1;

FIG. 3 is a schematic view of the electrical system of the electric fan system for a vehicle of FIG. 1;

FIG. 4 is a view of the electrical system of an electric fan drive circuit of the electric fan system for a vehicle of FIG. 1;

FIG. 5 is a flow chart of a fan control routine;

FIG. 6 is a graph of a control characteristic with respect to a water temperature of a brushless motor of a first electric fan;

FIG. 7 is a graph of a control characteristic with respect to a coolant pressure of a brushless motor of a first electric fan;

FIG. 8 is a graph of a control characteristic of a brush motor of a second electric fan;

FIG. 9 is a graph of a control characteristic of a brush motor of another embodiment;

FIG. 10 is a schematic view of the configuration of an electric fan system for a vehicle of another embodiment of the present invention;

FIG. 11 is a schematic view of the electrical system of the electric fan system for a vehicle of FIG. 10;

FIG. 12 is a flow chart of the control processing by an electronic control unit of FIG. 11;

FIG. 13 is a graph for determining a flow rate of an electric fan by an electronic control unit of FIG. 11;

FIG. 14 is a graph for determining a flow rate of an electric fan by an electronic control unit of FIG. 11;

FIG. 15 is a graph for determining a flow rate of an electric fan by an electronic control unit of FIG. 11;

FIG. 16 is a schematic view of the configuration of an electric fan system for a vehicle according to a modification of the present invention; and

FIG. 17 is a graph for determining the flow rate of an electric fan in the modification shown in FIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, preferred embodiments of the present invention will be explained with reference to the drawings. Throughout the drawings, the same reference numerals indicate the same objects.

First Embodiment

FIG. 1 to FIG. 4 show the configuration of an electric fan system for a vehicle according to a first embodiment of the present invention. FIG. 1 and FIG. 2 are schematic views of the configuration of the electric fan system for a vehicle.

The electric fan system for a vehicle is provided inside an engine compartment of the vehicle, as shown in FIG. 1, with first and second electric fans 10 and 20 comprised of axial flow fans. The first electric fan 10 is comprised of a rotor 11 and a brushless motor 12 for driving rotation of the rotor 11, while the second electric fan 20 is comprised of a rotor 21 and a brush motor (DC motor) 22 for driving rotation of the rotor 21.

The first and second electric fans 10 and 20 function to circulate cooling air to the radiator 100 and the condenser 110 forming the heat exchange unit so as to cool the radiator 100 and the condenser 110.

Further, the radiator 100 and the condenser 110 are arranged in the engine compartment in the front-rear direction of the vehicle. The radiator 100 cools the cooling water circulating inside a water-cooled engine for driving the vehicle (engine cooling water). The condenser 110 is one component of the vehicle air-conditioning system for air-conditioning of the inside of the vehicle compartment in a refrigeration cycle (refrigeration cycle system) and cools the coolant circulating through the inside of the vehicle air-conditioning system.

Note that the fan diameters of the rotors 11 and 21 of the first and second electric fans 10 and 20 are set to be substantially equal to each other. Due to this, it is possible to achieve a uniform flow rate of the cooling air (reduce the unevenness) over the entire surface of the heat exchange unit and possible to improve the cooling efficiency in the heat exchange unit.

Next, the schematic electrical system of the electric fan system for a vehicle of the present embodiment will be explained using FIG. 3 and FIG. 4. FIG. 3 is a block diagram showing the schematic electrical system of the electric fan system for a vehicle, while FIG. 4 is a block diagram showing details of the electric fan drive circuit in FIG. 3.

The electric fan system for a vehicle, as shown in FIG. 3, is comprised of an electric fan drive circuit 30 and an engine electronic control unit (E/G-ECU) 40. The electric fan drive circuit 30, as shown in FIG. 4, is comprised of a control unit 31, a brushless motor driver 32, and a brush motor driver 33.

The control unit 31 is comprised of a brushless motor control unit 31 a, a power logic generation circuit 31 b, and a brush motor control unit 31 c.

Here, the brushless motor control unit 31 a detects the actual position of a rotor 12 b of the brushless motor 12 based on detection output from a magnetic pole sensor 13 in the brushless motor 12. Note that the actual position of the rotor 12 b detected will be referred to below as the detected position of the rotor 12 b.

The magnetic pole sensor 13 is comprised of three Hall elements. The magnetic pole sensor 13 is arranged around the rotor 12 b in the brushless motor 12 and detects changes in the magnetic field accompanying rotation of the rotor 12 b. Further, the rotor 12 b is comprised of a permanent magnet and makes the rotor 11 turn by its rotation.

The brushless motor control unit 31 a detects the target speed of the brushless motor 12 as a control instruction value (brushless motor control instruction value I₁) based on a duty ratio Ds of a pulse signal sent from the engine electronic control unit 40.

Further, the power logic generation circuit 31 b drives a brushless motor driver 32 based on the detected position of the rotor 12 b so as to make the actual speed of the brushless motor 12 approach the target speed.

The brushless motor driver 32 is a known inverter circuit which is supplied with power from a DC power supply Ba and controls the three-phase AC power supplied to a stator coil 12 a of the brushless motor 12 and is comprised of six field effect transistors U+, V+, W+, U−, V−, and W− used to form a three-phase full wave bridge circuit.

Note that the brushless motor control instruction value I₁ is set by the later explained control characteristic graphs (FIG. 6 and FIG. 7). Due to the control instruction value, the brushless motor 12 is given a first drive voltage V1 as an average value and rotates by a predetermined target speed in accordance with the first drive voltage V1.

The brush motor control unit 31 c controls the brush motor driver 32 by pulse width modulation (PWM) in accordance with a control signal output from the engine electronic control unit 40 so as to give a predetermined target speed (brush motor control instruction value I₂) based on a later explained control characteristic graph (FIG. 8 or FIG. 9).

The brush motor driver 33 is comprised of a single field effect transistor which is supplied with power from a DC power supply Ba and controls the power to the brush motor 22. Due to this, the brush motor 22 is supplied with the second drive voltage V2 as an average value and operates by a predetermined target speed in accordance with the second drive voltage V2.

The engine electronic control unit 40 is comprised of a microcomputer, a memory, etc. and controls the first and second electric fans 10 and 20 through the electric fan drive circuit 30 based on the detection output of a water sensor 41 for detecting the temperature of the cooling water of an engine (not shown) and the detection output of a pressure sensor 42 for detecting the pressure of the coolant (coolant pressure) flowing through the condenser 110. The water temperature sensor 41 detects the water temperature of the cooling water flowing out from the radiator 100 and returning to the water-cooled engine.

Next, the operation of this embodiment will be explained using FIG. 5 to FIG. 8. FIG. 5 is a flow chart showing a fan control routine of the engine electronic control unit 40. The engine electronic control unit 40 runs a computer program stored in the memory in accordance with the flow chart shown in FIG. 5. This computer program is repeatedly run every predetermined time (control period).

First, at step S100, the temperature of the cooling water (hereinafter referred to as the water temperature Tw) is read from the water temperature sensor 41 and the coolant pressure Pc is read from the pressure sensor 42.

Next, at step S110, first and second duty ratios D1 and D2 of a pulse signal for controlling the first electric fan 10 and a third duty ratio D3 of a pulse signal for controlling the second electric fan 20 are determined based on the water temperature Tw, the coolant pressure Pc, and the control characteristic graphs of FIG. 6, FIG. 7, and FIG. 8 stored in advance in the memory.

Specifically, as the first duty ratio D1, as shown in FIG. 6, a value is selected set so as to monotonously increase from a duty ratio corresponding to the minimum speed Nf0 as the water temperature Tw becomes larger in the period from the temperature T1 to the temperature T2 (for example, 105° C.>T1). Due to this, a first drive voltage V1 is supplied to the brushless motor 12. Further, when the water temperature Tw is the temperature threshold value T2 or more, the first duty ratio D1 is set to a constant duty ratio corresponding to the fan speed NF2(1) and the constant value first maximum drive voltage VM1 is supplied to the brushless motor 12 in accordance with this.

Further, as the second duty ratio D2, as shown in FIG. 7, a value is selected set so as to monotonously increase from a duty ratio corresponding to the minimum speed Nf0 as the coolant pressure Pc becomes larger in the period from the pressure P1 to the pressure P2 (>P1). Due to this, a first drive voltage V1 is supplied to the brushless motor 12. Further, when the coolant pressure Pc is the pressure threshold value P2 or more, the first duty ratio D1 is set to a constant duty ratio corresponding to the fan speed number of rotations of the fan per second NF2(1) and, accompanied by this, the constant value first maximum drive voltage VM1 is supplied to the brushless motor 12. Hereinafter, the fan speed means the number of rotations of the fan.

In this way, the first and second duty ratios D1 and D2 are values showing the speed of the brushless motor 12. This corresponds to the speed of the first electric fan 10, that is, the flow rate. Note that the minimum speed Nf0 may also be zero (stopped) or a finite value.

FIG. 8 is a graph of the control characteristic of the brush motor 22 and also shows the control characteristic graphs of the brushless motor 12 of FIG. 6 and FIG. 7.

As shown in FIG. 8, the third duty ratio D3 is is selected as a value which monotonously increases along with the rise of the water temperature Tw in the period from the temperature T1 to the temperature T2 (>T1). Due to this, the second drive voltage V2 is supplied to the brush motor 22. Further, when the water temperature Tw is the temperature threshold value T2 or more, the third duty ratio D3 is set to a constant duty ratio and a constant value constituted by the second maximum drive voltage VM2 is supplied to the brush motor 22 in accordance with this.

Alternatively, the third duty ratio D3 (corresponding to the second drive voltage V2) is set so as to monotonously increase along with the rise of the coolant pressure Pc as shown in FIG. 8 and so as to become a constant duty ratio (corresponding to the second maximum drive voltage VM2) when the coolant pressure Pc is the pressure threshold value Pc or more.

Note that the third duty ratio D3 is a value indicating the speed of the brush motor 22. This corresponds to the speed, that is, flow rate, of the second electric fan 20.

Further, as shown in FIG. 8, the second drive voltage V2 and second maximum drive voltage VM2 supplied to the brush motor 22 are set so as to become lower than the first drive voltage V1 and the first maximum drive voltage VM1 supplied to the brushless motor 12. Due to this, it is possible to suppress hot air sneaking to the locations blown upon by the second electric fan 20 and to extend the lifetime of the brush motor 22.

Next, at step S120, the larger of the first and second duty ratios D1 and D2 determined from the water temperature Tw and the coolant pressure Pc is selected and used as the duty ratio Ds.

Further, at step S130, a pulse signal of this selected duty ratio Ds is output to the brushless motor control unit 31 a of the control unit 31 of the electric fan drive circuit 30.

Here, the brushless motor control unit 31 a detects the target speed based on the duty ratio Ds of the pulse signal, detects the detected position of the rotor 12 b based on the detection output from the magnetic pole sensor 13, generates a drive signal including the detected position of the rotor 12 b and the target speed, and outputs this to the power logic generation circuit 31 b.

Along with this, the power logic generation circuit 31 b individually switches the transistors U+, V+, W+, U−, V−, and W− forming the brushless motor driver 33 based on the drive signal from the brushless motor control unit 31 a so as to make the actual speed of the brushless motor 12 approach the target speed.

Further, these transistors U+, V+, W+, U−, V−, and W− supply three-phase AC power to the stator coil 12 a by the individual switching. Further, among the transistors U+, V+, W+, U−, V−, and W−, the low potential side transistors U−, V−, and W− are controlled by PWM based on the control of the power logic generation circuit 31 b.

Along with this, by control of the three-phase AC power supplied to the stator coil 12 a, the speed of the rotor 12 b and in turn the speed of the rotor 11 is controlled. Due to this, the speed of the rotor 11 is controlled based on the duty ratio Ds of the pulse signal.

That is, the first electric fan 10 can be made to send cooling air of the flow rate determined in accordance with the detection signals Tw and Pc to the radiator 100 and the condenser 110.

Further, at step S140, a pulse signal of the third duty ratio D3 determined above is output to the brush motor control unit 31 c of the control unit 31 of the electric fan drive circuit 30.

Along with this, the brush motor control unit 31 c controls the brush motor driver 33 so that the brush motor driver 33 drives the brush motor 22 to the target speed by the drive voltage V2 corresponding to the third duty ratio D3 of the pulse signal.

In this case, the second electric fan 20 can be made to send cooling air of the flow rate determined in accordance with the detection signal Tw (or Pc) to the radiator 100 and the condenser 110.

Due to this, the second electric fan 20 can send cooling air to the radiator 100 and the condenser 110 along with the first electric fan 10.

Below, the actions and effects of this embodiment will be explained.

According to this embodiment, while the first electric fan 10 is operating, the second electric fan 20 is also operating without stopping, so in the operating region of the second electric fan 20, unevenness of the distribution of the flow rate caused by hot air sneaking in to the front of the vehicle is suppressed. Due to this, it is possible to suppress a drop in the cooling efficiency in the heat exchange unit (radiator 100 and condenser 110).

Simultaneously, since the drive voltage V2 of the brush motor 22 of the second electric fan 20 is controlled to be smaller than drive voltage V1 of the brushless motor 12 of the first electric fan 10 at all times, it is possible to extend the lifetime of the brush motor 22 and possible to extend the lifetime of the electric fan system.

Modifications of First Embodiment

In the above embodiment, the second drive voltage V2 supplied to the brush motor 22 driving the second electric fan 20 was set so as to linearly increase in accordance with the increase in the water temperature Tw (or coolant pressure Pc) up to the temperature threshold value T2 (or pressure threshold value P2), but the invention is not limited to this. For example, as shown in FIG. 9, it is also possible to make the second drive voltage V2 increase stepwise in accordance with the increase in the water temperature Tw or coolant pressure Pc under condition of being lower than the first drive voltage V1.

In the above embodiment, the example was explained of setting the second drive voltage V2 supplied to the brush motor 22 driving the second electric fan 20 based on the water temperature Tw or coolant pressure Pc, but the invention is not limited to this. That is, in the same way as the method of determining the control instruction value of the brushless motor 12 constituted by the duty ratio Ds, it is also possible to make the larger of the third duty ratio D3(T) set in accordance with the water temperature Tw and the third duty ratio D3(P) set in accordance with the coolant pressure Pc in FIG. 8 the third duty ratio D3 and control the brush motor 22 based on this selected third duty ratio D3.

In the above embodiment, the example was explained of controlling the brushless motor 12 and the brush motor 22 driving the first and second electric fans 10 and 20 based on the water temperature Tw and/or the coolant pressure Pc, but the invention is not limited to this. It is also possible to control these in accordance with the engine speed, vehicle speed detected by a vehicle speed sensor 43 etc. Alternatively, it is also possible to control the motors 12 and 22 in accordance with the rates of change of the water temperature Tw and coolant pressure Pc.

Second Embodiment

FIG. 10 shows the configuration of an electric fan system for a vehicle according to a second embodiment of the present invention. FIG. 10 is a view showing the partial configuration in the engine compartment of a vehicle.

The electric fan system for a vehicle is provided with, as shown in FIG. 10, electric fans 10 and 20. The electric fans 10 and 10 are arranged inside the engine compartment in the front-rear direction at the front side of a water-cooled engine 300. The electric fan 10 is the same as that shown in FIG. 1 and is comprised of a rotor and a brushless motor for driving rotation of the rotor, while the electric fan 20 is comprised of a rotor and a brush motor for driving rotation of the rotor.

On the other hand, at the front side of the electric fans 10 and 20, a radiator 100 and a condenser 110 are arranged in parallel in the front-rear direction. The electric fans 10 and 20 function to send cooling air to the radiator 100 and the condenser 110 to cool the radiator 100 and the condenser 110.

Here, the radiator 100 is a heat exchanger for cooling the cooling water circulating inside the water-cooled engine 300. The condenser 110 is one component of the vehicle air-conditioning system for air-conditioning of the inside of the vehicle compartment in a refrigeration cycle (refrigeration cycle system) and cools the coolant circulating through the inside of the vehicle air-conditioning system.

At the left side of the water-cooled engine in the engine compartment, an electronic control unit (ECU) box 410 is arranged. This ECU box 410 holds an electronic control unit 40 (FIG. 11) for controlling the engine.

Next, the schematic electrical system of the electric fan system for a vehicle of the present embodiment will be explained using FIG. 11. FIG. 11 is a block diagram showing the schematic electrical system of the electric fan system for a vehicle.

The electric fan system for a vehicle, as shown in FIG. 11, is comprised of an engine electronic control unit (E/G-ECU) 40 a. The electronic control unit 40 a is comprised of a microcomputer, a memory, peripheral circuits, etc. and controls the electric actuators of the water-cooled engine 300. Further, the electronic control unit 40 a controls the electric fans 10 and 20 based on the detection output of a temperature sensor 60 for detecting the temperature of the cooling water of the engine. The temperature sensor 60 detects the temperature of the cooling water near the cooling water outlet of the radiator 100 or near the cooling water outlet of the engine 300.

Here, in the present embodiment, when using the electronic control unit 40 a to control the electric fans 10 and 20, in addition to the temperature sensor 60, the detection output of a temperature sensor 61 for detecting the surface temperature of an ECU box 410 as the part temperature is used.

Further, the electric fan system for a vehicle is provided with an electric fan drive circuit 30 a. This electric fan drive circuit 30 a is comprised of a control unit 31 a, a brushless motor driver 32 a, and a brush motor driver 33 a. The control unit 31 a controls the brushless motor driver 32 a and the brush motor driver 33 a based on control instruction values instructed from the electronic control unit 40 a.

The brush motor driver 33 a is supplied with power from the DC power supply Ba and gives voltage to the electric fan 20 to control its speed. Specifically, the brush motor driver 33 a adjusts the value of the voltage given to the brush motor 22 of the electric fan 20 so as to adjust the speed of the brush motor 22 and in turn the flow rate of the electric fan 20. That brush motor 22 is comprised of a known electric DC motor.

On the other hand, the brushless motor driver 33 a is provided with a known inverter circuit serving as a three-phase full wave bridge circuit supplied with power from the DC power supply Ba and generating three-phase AC power for supply to the brushless motor 12 and a control circuit controlling this inverter circuit by PWN and outputting a three-phase AC power to be supplied to the brushless motor 12 from the inverter circuit to the brushless motor 12. The brushless motor 12 is comprised of a three-phase synchronous device motor.

Next, the operation of this embodiment will be explained using FIG. 12 and FIG. 13. FIG. 12 is a flow chart of the processing for fan control by the electronic control unit 40 a. The electronic control unit 40 a runs a computer program stored in advance in accordance with the flow chart shown in FIG. 12.

First, the temperature of the cooling water (water temperature) is read from the temperature sensor 60 and the surface temperature of the ECU box 410 is read as the part temperature from the temperature sensor 61. Further, it is judged if the temperature of the cooling water (water temperature) is the threshold value Tw or more (step S121).

Here, when the temperature of the cooling water (water temperature) is less than a threshold value Tw (temperature of cooling water≦Tw), it is judged NO. That is, it is judged that it is not necessary for the electric fan 10 to cool the radiator 100 and the condenser 110.

Further, it is judged if the part temperature constituted by the surface temperature of the ECU box 410 is a threshold value Ta or more (step S122). When the part temperature is the threshold value Ta or more (part temperature≧Ta), it is judged YES. That is, it is judged that it is necessary for the electric fan 10 to cool the ECU box 410, that is, the electronic control unit 40 a itself.

In this case, in the following way, the fan speed (that is, flow rate) required for cooling the ECU box 410 by the electric fan 10 based on the control pattern A stored in advance in the memory is calculated as a control instruction value. Here, the control pattern A, as shown in FIG. 13, is a characteristic graph having an abscissa showing the part temperature and the ordinate showing the fan speed where the fan speed and the part temperature are specified one-to-one.

Here, in the control pattern A, when the part temperature is within the intermediate temperature range, the fan speed becomes higher the higher the part temperature. Further, when the part temperature is less than the intermediate temperature range, the fan speed becomes the constant value of zero. That is, the electric fan 10 enters the OFF state. On the other hand, when the part temperature is above the intermediate temperature range, the fan speed becomes a constant value.

Further, the fan speed corresponding to the detected temperature read from the temperature sensor 61 (part temperature) is determined based on this control pattern A and the thus determined fan speed is output as the duty ratio of the control pulse signal to the control unit 31 a of the electric fan drive circuit 30 a.

On the other hand, the control unit 31 a drives the brushless motor driver 32 a based on the duty ratio of the control pulse signal, so the brushless motor driver 32 a supplies three-phase AC power corresponding to the duty ratio to the brushless motor 12 of the electric fan 10.

Here, the three-phase AC power becomes larger as the duty ratio becomes larger, while the three-phase AC power becomes smaller as the duty ratio becomes smaller. Therefore, the speed of the brushless motor 12 becomes higher as the duty ratio becomes larger, and the speed of the brushless motor 12 becomes lower as the duty ratio becomes smaller.

Since the speed of the brushless motor 12 is controlled in this way, the fan speed of the electric fan 10 is controlled in accordance with the part temperature.

On the other hand, the electric fan 10 is arranged at the right side in the engine compartment and the rotor of the electric fan 10 turns clockwise, so the air blown by the rotor flows to the right side of the engine 300 as shown by the arrows Y1 in FIG. 10. Therefore, the air pressure in the space at the right side of the engine 300 becomes higher and relative to this the air pressure in the space at the left side of the engine 300 (that is, around the ECU box 410) becomes lower.

Therefore, outside air flows into the left side space from the front of the vehicle as shown by the arrow Y2. Here, the ECU box 410 (that is, the electronic control unit 40 a) is arranged in the left side space, so the ECU box 410 is cooled by the outside air flowing in from the front of the vehicle.

After this, the routine proceeds to step S129, wherein the operating state of the electric fan 20 is decided based on the control pattern C. This control pattern C, as shown in FIG. 14, is a characteristic graph having an abscissa showing the cooling water temperature and the ordinate showing the operating state of the electric fan 20 where the operating state of the electric fan 20 and the cooling water temperature are specified one-to-one.

Specifically, in the control pattern C, to avoid control hunting of the operating state of the electric fan 20, hysteresis is set between the cooling water temperature and the operating state. When the cooling water temperature becomes higher than the temperature Ty, the electric fan 20 enters the ON state. On the other hand, when the cooling water temperature becomes lower than the temperature Tx (<Ty), the electric fan 20 enters the OFF state.

Based on this control pattern C, the operating state of the electric fan 20 corresponding to the cooling water temperature read from the temperature sensor 60 is determined and the thus decided operating state is output as the duty ratio of the control pulse signal to the control unit 31 a of the electric fan drive circuit 30 a.

Here, when deciding on the ON state as the operating state, the duty ratio dn is determined, while when deciding on the OFF state as the operating state, the duty ratio df (not equal to dn) is determined.

On the other hand, the control unit 31 a drives the brush motor driver 33 a based on the duty ratio of the control pulse signal, so the brush motor driver 32 a controls the brush motor 22 of the electric fan 20 so as to correspond to that duty ratio.

Here, in the case of the duty ratio dn, the brush motor driver 33 a supplies a constant voltage to the brush motor 22, so the brush motor 22 operates at a constant speed. Therefore, the electric fan 20 operates by a constant fan speed, so the radiator 100 and the condenser 110 are cooled by the air blown from the electric fan 20.

On the other hand, in the case of the duty ratio df, the brush motor driver 32 a stops the supply of voltage to the brush motor 22, so the electric fan 20 stops the fan operation.

Further, when the temperature of the cooling water (water temperature) is the threshold value Tw or more at the above step S121 (temperature of cooling water>Tw), it is judged YES. That is, it is judged that it is necessary for the electric fan 10 to cool the radiator 100 and the condenser 110.

Next, the routine proceeds to step S125, where the fan speed (that is, flow rate) required for cooling the radiator 100 and the condenser 110 by the electric fan 10 based on the control pattern B stored in advance in the memory is calculated as a control instruction value. Here, the control pattern B, as shown in FIG. 14, is a characteristic graph having an abscissa showing the cooling water temperature and the ordinate showing the fan speed where the fan speed and the cooling water temperature are specified one-to-one.

Here, in the control pattern B, when the cooling water temperature is within the intermediate temperature range, the fan speed becomes higher the higher the cooling water temperature. Further, when the cooling water temperature is less than the intermediate temperature range, the fan speed becomes the constant value of zero. That is, the electric fan 10 enters the OFF state. On the other hand, when the cooling water temperature is above the intermediate temperature range, the fan speed becomes a constant value.

Further, the fan speed corresponding to the detected temperature read from the temperature sensor 60 (cooling water temperature) (hereinafter referred to as the “fan speed Kb”) is determined based on this control pattern B.

Next, it is judged if the part temperature (surface temperature of ECU box 410) is the threshold value Ta or more (step S126). Further, when the part temperature is less than the threshold value Ta (part temperature<Ta), it is judged NO. That is, it is judged that there is no need for the electric fan 10 to cool the ECU box 410, that is, the electronic control unit 40 a itself.

In this case, as explained above, the fan speed Kb determined based on the control pattern B is output as the duty ratio of the control pulse signal to the control unit 31 a of the electric fan drive circuit 30 a.

Therefore, the control unit 31 b drives the brushless motor driver 32 a based on the duty ratio Kb of the control pulse signal, so the brushless motor driver 32 a supplies three-phase AC power corresponding to the duty ratio to the brushless motor 12 of the electric fan 10.

Here, the speed of the brushless motor 12 is controlled so as to correspond to the duty ratio Kb, so the fan speed of the electric fan is controlled in accordance with the cooling water temperature. Further, the air from the electric fan 10 cools the radiator 100 and the condenser 110.

Here, explaining the relationship between the control patterns B and C, in the control pattern B, when the cooling water temperature is higher than the temperature TSB, the brushless motor 12 enters the ON state, while when the cooling water temperature is lower than the temperature TSB, the brushless motor 12 enters the OFF state.

On the other hand, in the control pattern C, when the cooling water temperature becomes higher than the temperature Ty, the electric fan 20 enters the ON state, while when the cooling water temperature becomes lower than the temperature Tx, the electric fan 20 enters the OFF state.

Further, since the temperatures Tx and Ty are set higher than the temperature TSB, in the low cooling water temperature region, only the electric fan 10 operates. When the cooling water temperature reaches the high temperature region, both the electric fans 10 and 20 operate. Due to this, the frequency of operation of the electric fan 10 becomes higher than the frequency of operation of the electric fan 20. That is, the electric fan 10 is operated preferentially over the electric fan 20.

Note that when the part temperature is the threshold value Ta or more at the above step S126 (part temperature≧Ta), it is judged YES. That is, it is judged that it is necessary to use the electric fan 10 to cool the ECU box 410, that is, the electronic control unit 40 itself.

In this case, in the same way as the processing for control of the above step S130, the fan speed of the electric fan 10 (hereinafter referred to as the “fan speed Ka”) is determined based on the control pattern A and the part temperature (step S127). Further, the higher of the fan speeds Ka and Kb is selected and the selected fan speed Kc is output as the duty ratio of the control pulse signal to the control unit 51 of the power fan drive circuit 50.

Therefore, the control unit 31 a drives the brushless motor driver 32 a based on the duty ratio Kc of the control pulse signal, so the brushless motor driver 32 a supplies three-phase AC powr corresponding to the duty ratio to the brushless motor 12 of the electric fan 10.

Here, since the speed of the brushless motor 12 is controlled so as to correspond to the duty ratio Kc, the fan speed of the electric fan 10 is controlled in accordance with the cooling water temperature and the part temperature. The air blown by the electric fan 10 cools all of the radiator 100, condenser 110, and ECU box 410 (electronic control unit 40 a).

After this, the routine proceeds to step S129, where processing is performed to control the brush motor 22. Note that at step S122, when the part temperature is less than a threshold value Ta (part temperature<Ta), it is judged NO, the operation of the electric fan 10 is prohibited, and the routine proceeds to step S129.

Below the actions and effects of this embodiment will be explained. That is, the electric fan system for a vehicle of this embodiment circulates cooling air to a radiator 100 for cooling cooling water circulating inside a water-cooled engine 300 for vehicle operation and a condenser 110 for cooling a coolant circulating inside a vehicle air-conditioning system. It is provided with an electric fan 10 for circulating cooling air to the radiator 100 and condenser 110 by operation of a brushless motor 12, an electric fan 20 for circulating cooling air to the radiator 100 and condenser 110 by a brush motor 22, and an electronic control unit 40 a for operating the electric fan 10 preferentially over the electric fan 20 based on the temperature of the engine cooling water, wherein the electric fan 10 is designed to cool the ECU box 410 (that is, the electronic control unit 40 a) in addition to the radiator 100 and the condenser 110.

According to the present embodiment, since the electric fan 10 is operated preferentially over the electric fan 20, the wear of the electric fan 20, that is, the wear of the brush motor 22, can be suppressed. Further, the electric fan 10 is made to also use cooling air to cool the ECU box 410 as one of the “other vehicle-mounted parts” besides the radiator 100 and the condenser 110. Therefore, it is possible to cool the ECU box 410 (other vehicle-mounted part) while extending the lifetime.

Here, the electronic control unit 40 a determines the fan speed (flow rate) of the electric fan 10 based on the surface temperature of the ECU box 410 and the temperature of the engine cooling water, so the radiator 100, condenser 110, and ECU box 410 (that is, the electronic control unit 40 a) can be suitably cooled.

Further, in the embodiment, rubber engine mounts 310 are arranged at the four corners of the water-cooled engine between the water-cooled engine 300 and chassis. The rubber engine mounts 310 function to suppress transmission of vibration of the water-cooled engine to the chassis.

Here, when the rubber engine mounts 310 become high in temperature, they deteriorate in characteristics, so cooling is required, but since the air blown from the electric fan 10 flows as shown by the arrows Y1 in FIG. 11, the rubber engine mounts 310 at the right side are cooled by the cooling air from the electric fan 10.

Modifications of Second Embodiment

In the above embodiment, the example was explained of using the temperature of the cooling water of the engine 300 when controlling the electric fans 10 and 20, but the invention is not limited to this. The coolant temperature or the coolant pressure may also be used. Further, any of the cooling water temperature, coolant temperature, and coolant pressure may be used in combination.

In the above embodiment, the example was explained of not causing the air blown from the electric fan 10 to directly strike the ECU box 410, but to lower the air pressure around the ECU box 410 and cool the ECU box 410 by the outside air flowing in from the sides of the vehicle, but instead of this it is also possible to make the air blown from the electric fan 10 directly strike the ECU box 410 so as to cool the ECU box 410.

In the above embodiment, the example was explained of employing the ECU box 410 as one of the “other vehicle-mounted parts”, detecting the surface temperature of the ECU box 410, and using the detected temperature to control the speed of the electric fan 10, but instead of this it is also possible to employ the headlamps or rubber engine mounts 310 as the “other vehicle-mounted part”, detect the temperature of the same, and use the detected temperature to control the speed of the electric fan 10.

For example, when cooling the headlamps 200 (specifically, the headlamps using light emitting diodes), as shown in FIG. 16, it is also possible to employ ducts D1 and D2 for blowing air from the electric fan 10 to the headlamps 200.

In the above embodiment, the example was explained of the electric fan 20 entering the ON state when the temperature of the cooling water becomes higher than the temperature Ty and the electric fan 20 entering the OFF state when the temperature of the cooling water becomes lower than the temperature Tx in accordance with the control pattern C, but the invention is not limited to this. Even if the temperature of the cooling water becomes lower than the temperature Ta, so long as to an extent where no wear of the brush motor 22 occurs, it is possible to operate the electric fan 20.

In the above embodiment, the example was explained of determining one of the ON state and OFF state of the operating states of the electric fan 20 based on the temperature of the cooling water, but the invention is not limited to this. It is also possible to make the fan speed of the electric fan 20 gradually rise along with the rise in temperature of the cooling water and make the fan speed of the electric fan 20 gradually fall along with the fall in temperature of the cooling water.

In this case, the relationship between the control patterns B and C becomes as shown in FIG. 17. That is, compared with the control pattern B, the inclination of the control pattern C is smaller. If the power supplied to the brush motor 22 is set lower than the power supplied to the brushless motor 12, the frequency of operation of the brushless motor 12 becomes higher compared with the frequency of operation of the brush motor 22.

That is, the brushless motor 12 is operated preferentially over the brush motor 22. Therefore, compared with the electrical wear of the brushless motor 12, the electric wear of the brush motor 22 can be reduced. Along with this, it is possible to suppress electrical wear of the electric fan 20 compared with the electric fan 10, so the lifetime can be extended.

In the second embodiment, the example was explained where the electric fan 10 (brushless motor 12) was arranged at the right side and the electric fan 20 (brush motor 22) was arranged at the left side, but the invention is not limited to this. It is also possible to arrange the electric fan 10 (brushless motor 12) at the left side and arrange the electric fan 20 (brush motor 22) at the right side.

Further, in working the invention, the fan rotational directions of the electric fans 10 and 20 may be freely set. Further, the other vehicle-mounted parts (for example, the ECU box 410) which have to be cooled may also be freely arranged.

Explaining the correspondence between the second embodiment and the claims, the electronic control unit 40 a corresponds to the control means.

While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention. 

1. An electric fan system for a vehicle which circulates cooling air to a heat exchange unit provided with a radiator for cooling cooling water circulating inside a water-cooled engine for vehicle operation and a condenser for cooling a coolant circulating inside a refrigeration cycle apparatus, the system comprising: a brushless motor driven by a first drive voltage, a first electric fan circulating cooling air to the heat exchange unit by the brushless motor, a brush motor driven by a second drive voltage, a second electric fan circulating cooling air to the heat exchange unit by the brush motor, and a control device supplying the brushless motor with the first drive voltage so that the first drive voltage monotonously increases up to a first maximum drive voltage in accordance with a rise in temperature of the cooling water and for supplying the brush motor with the second drive voltage so that the second drive voltage monotonously increases up to a second maximum drive voltage in accordance with a rise in temperature of the cooling water and becomes a voltage lower than the first drive voltage based on the detection output from a temperature sensor for detecting the temperature of the cooling water.
 2. An electric fan system for a vehicle as set forth in claim 1, wherein when the temperature of the cooling water is a temperature of a temperature threshold value or more, the first and second maximum drive voltages are set to become constant values.
 3. An electric fan system for a vehicle which circulates cooling air to a heat exchange unit provided with a radiator for cooling cooling water circulating inside a water-cooled engine for vehicle operation and a condenser for cooling a coolant circulating inside a refrigeration cycle apparatus, the system comprising: a brushless motor driven by a first drive voltage, a first electric fan circulating cooling air to the heat exchange unit by the brushless motor, a brush motor driven by a second drive voltage, a second electric fan for circulating cooling air to the heat exchange unit by the brush motor, and a control device for supplying the brushless motor with the first drive voltage so that the first drive voltage monotonously increases up to a first maximum drive voltage in accordance with a rise in pressure of the coolant and for supplying the brush motor with the second drive voltage so that the second drive voltage monotonously increases up to a second maximum drive voltage in accordance with a rise in pressure of the coolant and becomes a voltage lower than the first drive voltage based on the detection output from a pressure sensor for detecting the pressure of the coolant in the condenser.
 4. An electric fan system for a vehicle as set forth in claim 3, wherein when the pressure of the coolant is a pressure of a pressure threshold value or more, the first and second maximum drive voltages are set to become constant values.
 5. An electric fan system for a vehicle as set forth in claim 1, wherein both the first and second electric fans are axial flow fans and the fan diameters are substantially equal.
 6. An electric fan system for a vehicle which circulates cooling air to a heat exchange unit provided with a radiator for cooling cooling water circulating inside a water-cooled engine for vehicle operation and a condenser for cooling a coolant circulating inside a refrigeration cycle apparatus, the system comprising: a first electric fan circulating cooling air to the radiator and condenser by operation of a brushless motor, a second electric fan for circulating cooling air to the radiator and condenser by a brush motor, and a control means for operating the first electric fan preferentially over the second electric fan based on a state of either the cooling water and the coolant, the first electric fan being designed to cool other vehicle-mounted parts than the radiator and condenser by cooling air.
 7. An electric fan system for a vehicle as set forth in claim 6, wherein the control means determines the flow rate of cooling air by the first electric fan based on both the state of one of the cooling water and the coolant and the temperature of the other vehicle-mounted parts.
 8. An electric fan system for a vehicle as set forth in claim 6, wherein the first electric fan is designed to blow air toward locations different from the locations where the other vehicle-mounted parts are arranged. 